1.\" $OpenBSD: SSL_pending.3,v 1.4 2018/03/27 17:35:50 schwarze Exp $ 2.\" OpenSSL a528d4f0 Oct 27 13:40:11 2015 -0400 3.\" 4.\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>, 5.\" Bodo Moeller <bodo@openssl.org>, and Matt Caswell <matt@openssl.org>. 6.\" Copyright (c) 2000, 2005, 2015, 2016 The OpenSSL Project. 7.\" All rights reserved. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in 18.\" the documentation and/or other materials provided with the 19.\" distribution. 20.\" 21.\" 3. All advertising materials mentioning features or use of this 22.\" software must display the following acknowledgment: 23.\" "This product includes software developed by the OpenSSL Project 24.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 25.\" 26.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 27.\" endorse or promote products derived from this software without 28.\" prior written permission. For written permission, please contact 29.\" openssl-core@openssl.org. 30.\" 31.\" 5. Products derived from this software may not be called "OpenSSL" 32.\" nor may "OpenSSL" appear in their names without prior written 33.\" permission of the OpenSSL Project. 34.\" 35.\" 6. Redistributions of any form whatsoever must retain the following 36.\" acknowledgment: 37.\" "This product includes software developed by the OpenSSL Project 38.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 39.\" 40.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 41.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 42.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 43.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 44.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 45.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 46.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 47.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 49.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 50.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 51.\" OF THE POSSIBILITY OF SUCH DAMAGE. 52.\" 53.Dd $Mdocdate: March 27 2018 $ 54.Dt SSL_PENDING 3 55.Os 56.Sh NAME 57.Nm SSL_pending 58.Nd obtain number of readable bytes buffered in an SSL object 59.Sh SYNOPSIS 60.In openssl/ssl.h 61.Ft int 62.Fn SSL_pending "const SSL *ssl" 63.Sh DESCRIPTION 64Data is received in whole blocks known as records from the peer. 65A whole record is processed, for example decrypted, in one go and 66is buffered until it is read by the application via a call to 67.Xr SSL_read 3 . 68.Pp 69.Fn SSL_pending 70returns the number of bytes which are available inside 71.Fa ssl 72for immediate read. 73.Pp 74.Fn SSL_pending 75takes into account only bytes from the TLS/SSL record that is 76currently being processed (if any). 77If the 78.Fa ssl->read_ahead 79flag is set (see 80.Xr SSL_CTX_set_read_ahead 3 ) , 81additional protocol bytes beyond the current record may have been 82read containing more TLS/SSL records. 83This also applies to DTLS. 84These additional bytes will be buffered but will remain unprocessed 85until they are needed. 86As these bytes are still in an unprocessed state, 87.Fn SSL_pending 88will ignore them. 89Therefore it is possible for no more bytes to be readable from the 90underlying BIO (because the library has already read them) and for 91.Fn SSL_pending 92to return 0, even though readable application data bytes are available 93(because the data is in unprocessed buffered records). 94.Sh RETURN VALUES 95.Fn SSL_pending 96returns the number of buffered and processed application data 97bytes that are pending and are available for immediate read. 98.Sh SEE ALSO 99.Xr ssl 3 , 100.Xr SSL_CTX_set_read_ahead 3 , 101.Xr SSL_read 3 102.Sh HISTORY 103.Fn SSL_pending 104appeared in SSLeay 0.4 or earlier and has been available since 105.Ox 2.4 . 106.Sh BUGS 107Up to OpenSSL 0.9.6, 108.Fn SSL_pending 109did not check if the record type of pending data is application data. 110